Field of the Invention
The present invention relates generally to devices and methods for correcting vision and more particularly to ophthalmic device combinations for providing accommodative vision.
Description of the Related Art
The human eye includes an anterior chamber between the cornea and iris, a posterior chamber including a capsular bag containing a crystalline lens, a ciliary muscle, a vitreous chamber behind the lens containing the vitreous humor, and a retina at the rear of this chamber. The human eye has a natural accommodation ability. The contraction and relaxation of the ciliary muscle provides the eye with near, intermediate and distant vision. This ciliary muscle action shapes the natural crystalline lens to the appropriate optical configuration for focusing light rays entering the eye on the retina.
After the natural crystalline lens is removed, for example, because of cataract or other condition, a conventional, monofocal IOL can be placed in the posterior chamber. Such a conventional IOL has very limited, if any, accommodating ability. However, the wearer of such an IOL continues to require the ability to view both near and far (distant) objects. Corrective spectacles may be employed as a useful solution. Multifocal IOLs without accommodating movement have also been used to provide near/far vision correction.
Attempts have been made to provide IOLs with accommodating movement along the optical axis of the eye as an alternative to shape changing. Examples of such attempts are set forth in Levy U.S. Pat. No. 4,409,691, U.S. Pat. Nos. 5,674,282 and 5,496,366 to Cumming, U.S. Pat. No. 6,176,878 to Gwon et al, U.S. Pat. No. 6,231,603 to Lang et al, and U.S. Pat. No. 6,406,494 to Laguette et al. The disclosure of each of these patents is incorporated herein by reference.
One problem that exists with such IOLs is that they often cannot move sufficiently to obtain the desired accommodation. The degree of accommodation has been closely related to the lens prescription of the individual patient. In addition, the presence of such lenses can result in cell growth from the capsular bag onto the optics of such lenses. Such cell growth, often referred to as posterior capsule opacification (PCO), can interfere with the clarity of the optic to the detriment of the lens wearer's vision.
Another problem that can occur is that of providing an intraocular lens that provides a predetermined amount of accommodative power for a wide variety of eyes and with a relatively low amount of aberrations for both near and distant vision. This problem may arise because mechanical stresses used to change the focal length of a lens generally give rise to optical aberrations that reduce visual acuity of the eye. A related problem is that of determining a precise prescription for the aphakic eye prior to the surgical procedure for replacing the natural lens with an accommodative intraocular lens. This may result in implantation of an intraocular lens that is either too strong or too weak for the patient, or that does not produce enough accommodation to provide both near and distant vision. A similar problem may occur when the correct prescription is initially provided, but the patient's prescription changes over time.
It would be advantageous to provide IOLs adapted for accommodating movement and/or deformation, which can preferably achieve an acceptable amount of accommodation and/or a reduced risk of PCO. It would also be advantageous to provide accommodating intraocular lenses or systems of ophthalmic devices that accurately provide a patient's prescription for distant and/or near vision in a way that produces little or no optical aberrations.